This project concerns regulation of food intake and body weight as these pertain to obesity, and consists of the following components: (1) Further validation of conditioned salivation as a measure of appetite and hunger. (2) Use of conditioned salivation as a means of studying satiety mechanisms believed to be important. These include the action of the following: cholecystokinin, an intestinal hormone; hydrocycitrate, a compound which reduces lipogenesis and promotes glycogen production, and fenfluramine, an anorectic drug. (3) Investigation of the acquisition of anticipatory control of food intake by sensory qualities of food through a process of conditioning; learning of perferences for foods eaten under conditions of high levels of hunger drive; and aversion learning under the special condition which follow intestinal by-pass surgery. (4) Investigation of alternations in hunger and appetite as a result of weight loss which may operate to "defend" body weight. (5) Study of caloric regulation, hunger and appetite, spontaneous activity and patterns of parental reinforcement of activity level in obese and non-obese children. (6) Development of set measures of parameters of food regulation and energy expenditure in infants, with special attention to assessment of factors which would be expected to be predictors of later adiposity.